In general, a hydraulic system is mounted in construction equipment to operate various operating devices. The hydraulic system operates a hydraulic pump by receiving power from an engine, and various operating devices are operated by working oil discharged from the hydraulic pump. The working device includes an actuator operated by hydraulic pressure.
In the meantime, available torque generated by the engine is limited. Accordingly, an operating load applied to an operating device needs to be operated within a range of the available torque of the engine. When the operating load is close to or exceeds the range of the available torque of the engine, the operating load is hard on the engine. Particularly, in order to generate required torque, the large amount of fuel is momentarily consumed and exhaust gas is generated.
On the other hand, the maintenance of the engine at a rated engine speed even in a low operating load is inefficient in consideration of fuel efficiency. The reason is that when an operating device does not perform an operation or performs an operation having a very small operating load, torque generated by the engine is not used by the operating device and disappears.
As a technology for solving the aforementioned problem, there is an auto engine idle mode maintaining a minimum engine speed at a degree, at which the engine is not stopped. That is, the auto engine idle mode may be a state where the engine is operated, but torque at a degree substantially usable by an operating device is not generated. This is for the purpose of improving fuel efficiency of construction equipment by reducing an engine speed when engine torque is not used.
The auto engine idle mode known in the related art is varied according to whether a lever of a manipulating device is in a neutral state or an operating state, or whether an auto idle switch is selected.
The auto engine idle mode in the related art will be described in more detail below.
When the auto idle switch is in an off state, the engine maintains a high engine speed higher than the rated engine speed regardless of a neutral position or an operation position of the lever.
By contrast, when the auto idle switch is in an on state, the auto engine idle mode is executed only when the lever is at the neutral position, and the engine continuously maintains a high engine speed when the lever is at the operating position.
That is, an apparatus and a method for controlling an engine of construction equipment known in the related art have a problem in that a section, in which a fuel efficiency improvement effect is substantially expectable by the auto engine idle mode, is very limited.
Hereinafter, an apparatus and a method for controlling an engine of construction equipment according to the Comparative Example in the related art will be described in more detail with reference to FIGS. 1 to 3.
FIG. 1 is a diagram for describing an apparatus and a method for controlling an engine of construction equipment according to the Comparative Example. FIG. 2 is a diagram for describing a no-load (idle) section in the apparatus and the method for controlling the engine of construction equipment according to the Comparative Example. FIG. 3 is a diagram for describing an operation case in the no-load (idle) section in the apparatus and the method for controlling the engine of construction equipment according to the Comparative Example.
As illustrated in FIG. 1, reviewing a configuration for performing a control in an auto engine idle mode according to the Comparative Example, a first on/off signal of a lever 12, based on which an operation of construction equipment may be determined, and a second signal indicating whether an auto idle switch 14 is selected are provided to a vehicle control unit (VCU) 10. The VCU 10 generates an engine speed command by calculating an engine speed appropriate in a current situation. The engine speed command is provided to an engine control unit 22, and an engine 20 is operated by the engine speed command.
As illustrated in FIG. 2, in the Comparative Example, when a predetermined time is maintained in a neutral section of an operating device, the engine enters an auto engine idle mode. Here, the predetermined time may be generally set to be within a range from 3 seconds to 10 seconds.
That is, in the Comparative Example, when the lever 12 is not manipulated in a state where the auto idle switch 14 is on, and an engine speed is maintained at a high engine speed RH, a mode of the engine is switched into the engine idle mode. In the engine idle mode, an engine speed is changed into an idle engine speed RI. The idle engine speed RI means that a low engine speed at a degree, at which the engine is not stopped, is maintained as described above.
Then, when the lever 12 is operated, the idle engine speed RI is changed into the high engine speed RH, so that the engine generates large torque at a degree at which an operating device is operable.
In the meantime, when the high engine speed RH is changed into the idle engine speed RI or by contrast, the idle engine speed RI is restored to the high engine speed RH, an inclination of a change of an engine speed to a time is determined by a governing speed of the engine.
Referring to FIG. 3, there is a case where the method of controlling the engine of construction equipment according to the Comparative Example is rather disadvantageous in fuel efficiency.
That is, when the lever 12 is operated in the auto engine idle section, an engine speed is increased at a moment of the operation of the lever 12 to reach the high engine speed RH. Then, the engine speed is varied according to an operating load. For example, an operation of moving a boom up or folding an arm performs digging, which may be a high load operation. During the performance of the high load operation, an engine speed is maintained at a rated engine speed.
In the meantime, when construction equipment performs an operation of moving down the boom or swinging an upper body, the construction equipment may perform a relatively low load operation compared to the high load operation. As described above, during the performance of the low load operation, an engine speed is maintained at a high degree reaching the high engine speed RH.
That is, in the method for controlling the engine of construction equipment in the related art according to the Comparative Example, a high engine speed is rather generated in a low load operation section compared than a high load operation section, and as a result, fuel consumption is increased and fuel efficiency deteriorates. Further, an engine speed is maintained at the high engine speed RH, so that a noise problem is generated.